1) Field of the Invention
The present invention relates to a technique for updating an address book of a processing terminal (a processing apparatus), which retains address information on other processing terminals, to the latest state, in a communication system in which a plurality of processing terminals are communicably connected to one another.
2) Description of the Related Art
Recently spread are processing terminals (hereinafter, referred simply terminals) such as personal computers, PDA (Personal Digital Assistants), cellular phones and so forth, which can transmit/receive information (E-mails, speeches, etc.) to/from one another over a network.
Such processing terminal manages address information (hereinafter, referred to simply as addresses) used to specify other processing terminals in its address book.
In the case where a plurality of processing terminals transmit/receive electronic mails, mail addresses correspond to the address information. In the case where a plurality of processing terminals make speech calls by using IP (Internet Protocol) telephones or transmit/receive character messages by using instant messengers or the like, addresses (for example, IP addresses) for specifying relevant processing terminals correspond to the address information.
It is preferable that the state of the address book is updated when the user of other processing terminal changes his/her address, so that the address book is kept in the latest state.
Heretofore, update of the address book is executed by that the user makes transmission to each address retained in the address book to confirm whether to receive an appropriate response to the transmission.
Namely, the user confirms whether or not addresses retained in the address book are valid in the following manner. The user makes transmission to a certain address, determines that the address is valid when the processing terminal at the address appropriately responds (whether or not a communication with the processing terminal is established), and holds the address as it is in the address book. When the processing terminal at the address does not appropriately respond (when the communication with the processing terminal fails to be established), the user determines that the address is invalid, and makes the address in the address book invalid.
However, this manner is troublesome and time-wasting for the user to update the address book when the number of addresses retained in the address book is large.
To overcome this drawback, there has been proposed a technique (for example, refer to Patent Document 1 below) which, when a mail address of a certain terminal is updated, updates the mail address of the terminal in address books in other terminals, taking this opportunity.
According to the technique disclosed in Patent Document 1, when one terminal updates its mail address, contents of address books of other terminals are automatically updated. For this, other terminals have to have a function of accepting (permitting) an instruction for updating the mail address in its address book given from the outside, and a function of updating its address book according to the instruction.
It is not efficient to provide such the functions to all terminals in a network system in which an enormous number of terminals are communicably connected to transmit/receive mails through a plurality of mail servers.
According to the technique disclosed in Patent Document 1, other terminals to which the changed mail address of a certain terminal is to be notified are designated on the basis of an address book retained by the terminal whose mail address has been changed. For this, even if there is a terminal to which the user does not want to notify of his/her changed mail address, the new mail address is unintentionally notified to the terminal so long as an address of the terminal is retained in the user's address book. Thus, the technique disclosed in Patent Document 1 has low versatility.
If a certain terminal can choose another terminal to which the new address is to be notified, the invalid old address remains unchanged and retained in an address book of the latter terminal that has not received the notification (that is, the terminal to which the former terminal has not notified of the address change), so that the address book of the latter terminal remains un-updated.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2005-033733